Remove GCC redundant-decls workaround for mbedtls_ct_memcmp

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index 5879e47..1411e14 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -476,10 +476,12 @@
                               size_t offset_max,
                               size_t len);
 
-/* Documented in include/mbedtls/constant_time.h. a and b are secret. */
-int mbedtls_ct_memcmp(const void *a,
-                      const void *b,
-                      size_t n);
+/* Documented in include/mbedtls/constant_time.h. a and b are secret.
+
+   int mbedtls_ct_memcmp(const void *a,
+                         const void *b,
+                         size_t n);
+ */
 
 #ifdef __GNUC__
     #pragma GCC diagnostic pop